One of the most significant metrics for space propulsion systems is specific impulse, which is the ratio of thrust produced to the rate of propellant consumed. Specific impulse has units of seconds, and is essentially the number of seconds that a pound of propellant will produce a pound of thrust. The higher the specific impulse the less propellant mass and associated tankage required for a given space mission. The Stafford Synthesis Group (Stafford, America at the Threshold) concluded that future space exploration will require advanced propulsion technologies. Subsequently, NASA conducted the Breakthrough Propulsion Physics Program (NASA/TM-1998-208400), one of the three main goals of which was to “discover new propulsion methods that eliminate or dramatically reduce the need for propellant. This implies discovering fundamentally new ways to create motion, presumably by manipulating inertia, gravity, or by any other interactions between matter, fields, and spacetime.” Therefore, an electromagnetic spacecraft propulsion system such as the present invention, that does not require expendable propellant and thus has an effectively infinite specific impulse, would address these needs and greatly reduce the cost of doing business in space.
Sir Isaac Newton's well-known Third Law of Motion, which states “To every action there is always an opposed equal reaction; or, the mutual actions of two bodies upon each other are always equal and directed to contrary parts”, has been interpreted as all-encompassing for over three hundred years. The Newtonian interpretation excluded the possibility of “reactionless propulsion” of a solid body. However, the discovery of electricity and magnetism, the new branch of electrodynamics resulting from Maxwell's Equations, and the subsequent rise of relativistic electrodynamics and quantum electrodynamics, led to a new interpretation of the famous “Third Law of Motion”.
One of the important characteristics of an electromagnetic (EM) wave is that it can transport energy from point to point. The rate of energy flow per unit area in a plane electromagnetic wave is described by the Poynting Vector S, defined as the cross-product of the instantaneous E-field and B-field comprising the EM wave. The direction of S gives the direction in which the energy moves. (Resnick and Halliday, Physics Parts I and II). Less familiar is the fact that EM waves also transport linear momentum. Just as Poincare noted in 1900, Stebens explains that the electromagnetic field closely resembles a relativistic fluid, composed of quantum, particles (photons), which transmits properties and responds to forces in much the same way as an Eulerian fluid (Stebens, Forces on Fields). In electromagnetism, as in Newton's solid body mechanics, the force on matter from the electromagnetic field is balanced by an equal and opposite force from matter on the field. Stebens presents an excellent proof which can be derived from Maxwell's equations and the Lorentz force law. The proof relates the reaction momentum change of the electromagnetic field to the time rate of change of the Poynting Vector, the divergence of the Maxwell Stress Tensor, and Einstein's relativistic mass-energy relation (Forces and Fields, op. cit.). By recognizing that electromagnetic fields can transport both energy and momentum, apparent “violations” of the Third Law are mathematically resolved by including modern field transport physics in the analysis of the reaction process.
Field propulsion, which employs electromagnetic field effects for generating propulsion forces, expels no reaction mass, and therefore effectively has an infinite specific impulse. As is well known to anyone skilled in the art, a moving charged particle generates a magnetic field. It is also well known that a magnetic field generates a force on a moving charged particle, namely the magnetic component of the full Lorentz Force, which component is proportional to the vector cross-product of the particle velocity vector and the magnetic field vector at the particle location. A common example is the well-known mutual equal-and-opposite forces on parallel conductors, which may be calculated by anyone skilled in the art through the use of the Biot-Savart Law. Prior to modern electrodynamics, the required compliance with Newton's Third Law (NTL), it has previously been accepted that the aforementioned magnetic interactions could not be used to produce a propellantless propulsion system. As discussed above, modern electrodynamics has shown that this is no longer a valid assumption.
Physicists have known since at least 1952 that apparent violations of NTL, in cases where force interactions involve charged particles and electromagnetic fields, simply do not account for the momentum carried in the fields themselves. As noted by Cullwick over sixty years ago: “The following simple relations between electromagnetic momentum, the Poynting vector for energy transport, and mass-energy equivalence do not appear to have received general recognition in connection with the validity of Newton's Third Law when applied to electromagnetic forces (Cullwick, Nature).” Since then, over thirty US patents and at least two dozen foreign patents have been issued for propellantless propulsion devices. Most importantly, recent experimental investigations conducted by NASA with an EM drive device (White, AIAA Journal of Propulsion and Power) have definitively confirmed that EM field propulsion is a reality.
Nobel Laureate Richard Feynman (The Feynman Lectures on Physics), among others, noted that the magnetic interaction between two charged particles moving orthogonally to each other apparently does not satisfy NTL in classical Newtonian dynamics. But, as discussed above, if the changing momentum of the electromagnetic fields of the two particles is included, then overall momentum is conserved. Engineering exploitation of this situation, to date, has not been effected due to the “circuit completion” problem. While isolated moving charges may apparently violate NTL, when they are considered as part of a complete closed circuit by application of Gauss' Law, the net forces on each circuit are found to be equal and opposite in accordance with NTL.
Prior Art for Electromagnetic Propulsion
The electrokinetic phenomenon known in the scientific literature as the Biefeld-Brown Effect, wherein electrical energy input into asymmetrical capacitors can be converted to mechanical energy, provides a reactionless force for propelling an object. T. T. Brown, a co-discoverer of the Biefeld-Brown Effect, has been issued U.S. Pat. No. 2,949,550, U.S. Pat. No. 3,018,394, and U.S. Pat. No. 3,187,206 for devices based on utilization of the effect. Townsend's colleague A. H. Bahnson has similarly been issued U.S. Pat. No. 2,958,790 U.S. Pat. No. 3,223,038, and U.S. Pat. No. 3,227,901 utilizing the effect. NASA is still experimentally investigating the use of Brown's discovery, as disclosed in U.S. Pat. No. 6,317,310, U.S. Pat. No. 6,411,493, and U.S. Pat. No. 6,775,123 to Campbell (assigned to NASA). Another such device is disclosed in U.S. Pat. No. 6,492,784 to Serrano, which generates the Biefeld-Brown Effect using stacked-disc asymmetrical capacitors, and which has just been approved for spaceflight testing. Debate is ongoing in the literature as to whether the Biefeld-Brown Effect will work in the vacuum of space. Another limiting consideration for using the effect may be the scalability potential, since asymmetrical capacitor devices to date have only generated tens of milli-newtons of thrust from tens of watts of input power.
Electrodynamic structures, as disclosed in U.S. Pat. No. 7,913,954 to Levin, include a power system, a plurality of collectors, a plurality of emitters, and conductive paths for moving payloads through the Earth's magnetic field. The inertial propulsion device disclosed in U.S. Pat. No. 8,066,226 to Fiala utilizes several interconnected gyroscopic elements within Earth's gravity field to move without propellant. U.S. Pat. No. 5,377,936 to Mitchell, discloses a method for using the electromagnetic spectrum particles which continually irradiate the earth from space for gravity guidance and propulsion of geosynchronous satellites, and other satellites and space vehicles within the gravitational influence of the earth. The superconducting electromagnetic turbine, as disclosed in U.S. Pat. No. 8,575,790 to Ogilvie, uses a pair of counter-rotating electrodynamic superconductor rotors to displace the surrounding geomagnetic field. These devices do not have general space-based utility because they are restricted to operations within either the gravity field or the magnetic field of Earth.
Other approaches to propellantless propulsion include mechanical devices such as U.S. Pat. No. 2,886,976 to Dean, which discloses a device for converting rotary motion into unidirectional motion. Similarly, U.S. Pat. No. 5,182,958 to Black discloses a mechanical device with wheels inside comprising both a nonlinear propulsion as well as an energy conversion system. A device for propellantless propulsion using radiated electromagnetic fields is disclosed in U.S. Pat. No. 5,142,861 to Schlicher et al., comprising an electromagnetic propulsion system based on an extremely low frequency radiating antenna structure driven by a matched high current pulsed power supply. U.S. Pat. No. 5,197,279 to Taylor also discloses an engine for imparting momentum to a vehicle by generating and transmitting in predetermined directions massive quantities of electromagnetic field energy in successive pulses.
Field modification approaches to propellantless propulsion include apparent reductions in gravitational mass or inertial mass. U.S. Pat. No. 3,626,605 to Wallace discloses a method and apparatus for generating a time-variant non-electromagnetic force field due to the relative motion of moving bodies constituted of elements whose nuclei have half integral “spin” values, with said force field exhibiting itself in the form of an induced secondary gravitational force. U.S. Pat. No. 5,280,864 to Woodward discloses a method for producing transient fluctuations in the inertial masses of material objects by employing an effect that is a consequence of relativistic theories of gravitation. Applying pulsed thrust synchronously with the mass fluctuations thus produced facilitate the transport of massive objects. Also to Woodward, both U.S. Pat. No. 6,098,924 and U.S. Pat. No. 6,347,766 disclose inventions for producing propellantless thrust by using piezoelectric force transducers attached to resonant mechanical structures, in accordance with Mach's principle and local Lorentz-invariance predictions of transient rest mass fluctuations in accelerated objects.
The most current example of a propellantless field propulsion system is an electromagnetic drive system as disclosed in British Patents GB2229865, GB2334761, GB2399601 and UK Patent Application GB2537119 to Shawyer, as well as U.S. Pat. Appl. No. 20140013724 to Fetta. This system includes an axially-asymmetric resonant cavity with a conductive inner surface adapted to support a standing electromagnetic (EM) wave. The internal standing EM wave induces a unidirectional force on the resonant cavity, thus generating thrust without reaction mass. Experimental versions of these EM devices have produced thrust levels of micro-newtons up to milli-newtons from several kilowatts of input power (AMA Journal of Propulsion and Power, op. cit.)